This invention relates to a process and apparatus for the separation of a low-boiling gaseous mixture by two-stage low-temperature rectification.
In conventional processes of this type, it is in most cases conventional to adjust the pressures in both stages so that the light fraction of the high-pressure stage is condensed in indirect heat exchange contact with the evaporating, heavy fraction of the low-pressure stage. More detailed information can be found in "Chemie-Ingenieur-Technik" [Chemical Engineers' Technology] 46 (1974) : 881-924. The pressure in the low-pressure stage is designed to be just so high that the products withdrawn from the head of this stage can be discharged from the plant against the frictional flow resistance of the pipelines. Especially in low-temperature separation plants having very large throughput quantities wherein the refrigerating losses are minor as compared to the compression energy to be expended, the total energy consumption is determined to a considerable part by the amount of energy necessary to compress the feed gas to the pressure of the high-pressure stage.